OB is a bacterial disease characterised by infertility in rams.
Unlike brucellosis in cattle, of which Australia is now officially free, OB is not considered a human health concern.
In some cases, the presence of OB in a flock may go unrecognised because of other causes of a poor lamb marking percentage.
However, once a significant portion of rams in a flock are infected, OB can lead to a substantial loss in production.
OB causes inflammation of the epididymis, which is the tube in which sperm are transported from the testis.
This inflammation leads to a complete or partial blockage of the epididymis leaving the ram sterile or with low fertility.
One way of diagnosing OB is to palpate or feel the testis of a ram for swellings.
OB can also be diagnosed by a blood test.
OB is typically introduced into a flock by an infected ram.
The disease subsequently spreads ram to ram or via ewes during joining.
Once introduced the only solution is to eradicate the disease.
This is achieved with veterinary assistance by palpating and blood testing rams and culling infected rams, because once a ram is infected with OB it will not recover.
As always prevention is better than cure — to assist in identifying low risk flocks a voluntary accreditation scheme is in place.
Your property can become OB accredited in consultation with your private veterinary practitioner by successively testing all rams over six months of age with clear results and demonstrating secure boundary fencing.
When purchasing replacement rams, OB accredited flocks provide the safest choice.
All boundary fencing should be secure to prevent straying to or from neighbouring properties.
For more information please contact your local veterinarian or Agriculture Victoria Veterinary or Animal Health Officer, or in NSW your Local Land Services.
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